1. Field of the Invention
The present invention relates to image signal recording systems, and more particularly to an image signal recording system for storing image signals of full-motion pictures or still pictures onto removable storage media.
2. Description of Related Art
An image signal recording system for storing full-motion picture image signals or still picture image signals is reported in IEEE Transaction on Consumer Electronics, Vol. 42, No. 3, August 1996, p. 776-p. 779, for example, in which image signals acquired through an image sensor or image signals received from an external image signal source such as VCR are converted into digital signals and then, after correction of a picture size and the number of vertical lines, these digital signals are stored as full-motion or still picture data.
In Japanese Non-examined Patent Publication No. 253251/1994, there is also disclosed a digital camera which has a compact circuit including a line memory and a frame memory for compressing full-motion pictures or still pictures and storing them onto a removable memory card.
As a removable memory card, there is a PC card meeting the PC Card Standards. For storing data, a hard disk card, SRAM card, flash memory card, etc. are available.
As a full-motion picture data compression method, the MPEG (Moving Picture coding Experts Group) 1 and MPEG2 are standardized, for example. Even in the MPEG1 which provides relatively slow transfer of data, a write data transfer rate of approx. 1.5 Mbits/s is employed in common applications. For realtime recording, it is required for a storage medium to support a write data transfer rate sufficiently higher than that of image signals.
A write data transfer rate of said hard disk card and SRAM card is approx. 15 Mbits/s, which poses no problem in image data storage, whereas a write data transfer rate of most types of flash memory cards having ATA interface is less than 1 Mbit/s, which is not suitable for storage of full-motion picture data. Even for still picture data, a certain limitation is imposed inconveniently on an interval between shots in a continuous shot operation due to an inadequate write data transfer rate of a storage medium employed.
Conventionally, however, any arrangement applicable to write data transfer rates of various kinds of general-purpose storage media has not been devised yet.
It is therefore an object of the present invention to obviate the abovementioned disadvantage by providing an image signal recording system which is capable of performing optimum storage setting for full-motion or still picture data to meet a write data transfer rate of each kind of storage medium employed.
In accomplishing this object of the present invention and according one aspect thereof, there is provided an image signal recording system comprising data transfer rate detecting means for detecting a write data transfer rate of each kind of storage medium employed and recording mode selector means for selecting an optimum recording mode for said storage medium based on the detected write data transfer rate thereof.